dgantz, You simply MUST:
1. Load as if for Travel
2. Get at least Front and Rear Axle WEIGHTS. A truck stop CAT scale will do that. Four Corner Weights are better but the scale is harder to find. Call a commercial scale sales/service company and see if they can ID one that will weigh you.
3. Adjust Tire Pressure (especially FRONT) to Actual Weight using a Load/Pressure Chart, and I doubt Front pressure will be more than around 55.
4. If you still don't like it, get a Front End Alignment and ask that CASTER be set toward the top of the range NOT the middle like most do. You want at least 5* on the Left. The Right should then be at least 5.5*
5. Make sure there is no play in the tow rig. A "drop receiver" is a top suspect. You want less than 1/2" "side slop" in the tow bar, receiver, connections to the towed vehicle, etc. If your towed vehicle has a badly worn front suspension/steering, it will try to weave behind the coach and throw it off track.
THEN go try again.
A Rear Track Bar is probably the most helpful for the issue you're having. SuperSteer has one, so does BlueOX, and Brazzel's does as well.